Positioning systems and techniques enable the location of devices to be determined and utilized to provide useful services. For example, the global positioning system (GPS) uses signals from a constellation of satellites to localize a receiver to within a few tens of meters. However, whilst systems such as GPS work effectively in open, outdoor environments, they typically do not operate well in indoor environments due to a lack of line-of-sight to the satellites.
Whilst alternative positioning techniques, such as those based on cell site identities can be used indoors, these techniques tend to have a lower accuracy than GPS and are more unpredictable due to uneven radio propagation. As location-based services become more pervasive and useful, it is therefore beneficial to be able to determine the position of a mobile device in indoor environments, without the addition of complex or expensive infrastructure or hardware at the mobile device.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known positioning techniques.